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Thyroid Antibody

Does this test have other names?

TPO Abs, Tg Abs, TSH-Rs Abs

What is this test?

This test measures the amount of thyroid antibodies in your blood. The test can help find out whether you have a problem with your thyroid.

Your thyroid is a butterfly-shaped gland located near the base of your throat above your collarbone. The thyroid makes two hormones, T3 and T4. These hormones affect your energy levels, mood, weight, and other important aspects of your health.

In some people, the immune system makes antibodies that affect the thyroid gland, causing health problems. These antibodies may target:

  • Thyroid peroxidase (TPO). This can lead to a condition called Hashimoto's thyroiditis. This condition causes hypothyroidism, or underactive thyroid.

  • Thyroglobulin (Tg). This substance in the thyroid plays a role in T3 and T4 production. Almost everyone with Hashimoto's thyroiditis has high levels of antibodies against TPO and Tg.

  • Thyroid-stimulating hormone (TSH) receptor. This can cause a condition called Graves' disease, leading to hyperthyroidism, or overactive thyroid.

Why do I need this test?

You might have this test if your doctor suspects that you have Graves' disease or Hashimoto's thyroiditis.

Symptoms of Graves' disease include:

  • Bulging eyes

  • Eye symptoms like irritation, pressure, and trouble moving eyes

  • Irritability

  • Nervousness

  • Weight loss

  • Extreme tiredness

  • Muscle weakness

  • Low tolerance for heat

  • Trouble sleeping

  • Tremors in the hands

  • Irregular heartbeat

  • Diarrhea

  • Redness and swelling on shins

  • Swollen thyroid, called goiter

Symptoms of Hashimoto's thyroiditis include:

  • Goiter that shrinks over time

  • Extreme tiredness

  • Low tolerance for cold

  • Weight gain

  • Body and joint pain

  • Hair loss

  • Constipation

  • Irregular menstrual periods

  • Depression

  • Slower heart rate

What other tests might I have along with this test?

Your doctor may order other tests, including:

  • Measurement of TSH, which is made by your pituitary gland. TSH regulates how much thyroid hormone your thyroid makes.

  • Measurement of free T4

  • Measurement of free T3

  • Radioactive iodine uptake test and thyroid scan, for Graves' disease

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

Normal results are negative, meaning that no antibodies against TPO, Tg, or TSH were found. You likely don't have a problem with your thyroid.

If your results show antibodies against TPO or Tg, it means you may have Hashimoto's thyroiditis.

If your results show antibodies against TSH receptor, it means you may have Graves' disease.

People with type 1 diabetes or certain autoimmune diseases, and pregnant women are more likely to have antibodies against the thyroid.

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

What might affect my test results?

Certain medications can affect your results. Being pregnant can affect your results.

How do I get ready for this test?

You don't need to prepare for this test. But be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.